CHEYENNE — Hemorrhagic disease caused by two possible viruses has been killing dozens of white-tailed deer in Wyoming and Montana over the past month.
The deer are dying of internal bleeding, and tests at the Wyoming State Veterinary Lab in Laramie will determine if epizootic hemorrhagic disease or bluetongue is responsible. Both viruses are endemic, or native, to the region and cause outbreaks in wildlife from time to time.
White-tailed deer are the usual victims, but hemorrhagic disease also can infect pronghorn antelope, elk and mule deer. Both diseases can infect livestock but neither poses a risk to humans.
People in recent weeks have come across dozens of dead and dying deer in the Big Horn Basin in north-central Wyoming and in Montana, from the Great Falls area to north of Chester.
“A lot of the landowners are finding them in the irrigation ditches,” Tom Easterly, a Wyoming Game and Fish Department wildlife biologist in Greybull, said Wednesday.
The actual number of deaths is difficult for biologists to determine with much accuracy. An especially large outbreak could cause the Wyoming Game and Fish Department to restrict deer hunting limits in the area this fall, Easterly said, but he expressed doubt that would happen.
Biting gnats spread hemorrhagic disease, and outbreaks tend to occur as dry weather causes deer and gnats to congregate near water.
Symptoms can include bleeding or swelling of the head, neck, tongue, or eyes, and victims suffer from loss of appetite and extreme weakness. Cases tend to taper off after the first hard freeze.
Last year, drought conditions led to hemorrhagic disease outbreaks in eastern Wyoming and a high rate of deer mortality in South Dakota and Nebraska, according to the department.
Epizootic hemorrhagic disease was first identified in Wyoming when significant numbers of deer died in the Black Hills north of Newcastle in 1957.